1902] MICROSCOPICAL JOURNAL. 15 
stalks that spring from the eyes of the potato grow into 
the potato-plant, Solanum tuberosum, and put out leaves 
and flower buds, while other so-called buds in the lower 
part of the stalks push out underground stems. But 
these undergrown stems never develop potatoes unless a 
fungus or fusarium is present, and this fusarium is al- 
‘ ways present in the skin of what are known as potatoes. 
In May, the terminal buds of the stems cease to throw 
out sprouts. They become hypertrophied and form tu- 
bers in which the larger part of the nourishment sent to 
them is stored up. The aerial buds are now almost com- 
pletely arrested in their growth. M. Henri Conpin who 
who records M. Bernard’s discoveries in La Nature says: 
‘‘We see that these two periods are characterized by two 
different modes of growth of the young buds. This must 
be attributed not to an alteration of condition in certain 
buds, but to a general modification of the state of the 
plant, of which the tuberculization of the terminal buds 
is the essential symptom.” : 
The causes of these modifications may be ascertained by 
a microscopic study of the roots. We shall see that in 
the second period, these are surrounded by the filaments— 
mycelium of a fungus of the genus Fugarium. This is 
never absent, It also exists\normally in the skin of the 
tubers, but not in the interior. This fusarium easily lives 
as a saprophyte in various culture mediums, For exam- 
ple, it impacts dung rapidly and throughout its whole 
mass. It may be noted that frequently in the cultivation 
of the potato, dung is utilized by placing it around each 
seed-potato. This method which is recommended by Par- 
-mentier, is evidently favorable to the propagation of the 
mycelium. 
The roots of the potato are long and ramified and their 
development is very rapid; they grow in all directions 
away from the seed-tubercle; infection is consequently 
irregular. This proceedure explains the irregularity 
